Ni-P alloy coatings were electroplated from nickel citric baths, and their hydrogen evolution reaction in acid electrolytes was studied. Experimental results show that all Ni-P deposits studied were amorphous, and exhibited excellent electrocatalytic activity and corrosion resistance in acid electrolytes. The deposit phosphorus content hardly changed with the electroplating current density, whereas the electrocatalytic activity of the deposit increased with increasing electroplating current density. Moreover, the deposit that absorbed more hydrogen during cathodic polarization exhibited better electrocatalytic activity. Finally, the electrocatalytic activity of the deposit became poor when measured in the electrolytes at higher temperatures. This is likely to be due to the formation of a surface oxide film in the high-temperature electrolyte.